The autochrome process was discovered by the brothers Auguste and Louis
Lumiere of Lyons in France. It was patented in 1904;
1906 in the USA.

The process was made commercially available from 1907 until
about 1940.

Process

Autochrome
was the first generally available process for colour photography.

The Lumiere
brothers' company sold Autochrome glass plates is sizes from under 2 ins x 2 ins up
to 15 ins x 18 ins.

Creating the Plate

1. To create the plates:

a) miniscule grains of potato starch were died,
some green, some red-orange, and some blue violet, then all three colours
were well mixed.

b) the glass slide was coated with varnish, then a
thin layer of the mixed coloured starch was added.

c) a further coat of varnish was added.

d) the slide was then coated with a layer of
orthochromatic gelatin bromide emulsion.

Exposing the Plate

2. The slide was exposed in the camera, with the
emulsion side furthest from the lens, so that the light had to pass
through the starch before reaching the film. [The starch acted as a
filter and so recorded the intensity of light in each of the three
colours.

Processing the Plate

3. The plate was then processed in the darkroom to
produce a slide with a positive image (i.e. developed, washed, bleached,
exposed, re-developed, washed and fixed).

For further comments see 'In Edinburgh - 1910' below

Result

The Image

The autochrome process produced a
coloured transparency on glass, with luminous colours.